A battery pack may include one or more contactors for selectively electrically coupling a battery pack output to an electrical load that is external to the battery pack. In some battery pack configurations, one contactor may be allocated to controlling a pre-charge circuit which includes a current limiting resistor in series with the battery pack output terminals. The pre-charge circuit allows the battery pack to supply a limited amount of current to a vehicle power grid or bus such that the bus can be charged without a large in-rush current. Once the vehicle power bus is charged a second contactor is engaged directly coupling battery cells to the vehicle bus. In this way, it is possible to limit current in-rush during vehicle power up so that vehicle side power control components do not have to be significantly over-sized.
One way of controlling the battery pack output contactors is to have a vehicle controller send a power request or a close contactor request to the battery pack controller. When the battery controller receives the power request, the contactors are closed providing power to the vehicle power bus. This configuration allows the vehicle controller to couple or uncouple electrical devices from the vehicle power bus before power is applied to the vehicle power bus. Thus, the vehicle controller can set the vehicle power bus in a state that is appropriate for accepting charge from the battery. However, during a vehicle reset condition or during vehicle controller degradation, it may be possible for the vehicle controller to request closure of battery pack output contactors when the vehicle bus is not in a condition desirable for closing contactors. If the battery pack contactors are closed when the vehicle power bus is not configured for a contactor closing operation, degradation of the contactor or pre-charge resistor or vehicle components may occur.
The inventors herein have recognized that it may be desirable to follow a procedure before closing battery pack output contactors. Accordingly, the inventors herein have developed a method for controlling output of a battery pack having a battery control module and a battery pack output contactor, comprising: resetting said battery control module; powering-up said battery control module from reset; receiving a request from an external controller to open the battery pack output contactor in the powered-up battery control module; and closing the battery pack output contactor after the reset only in response to the receiving request being a first instruction received from the external controller since the reset.
By first requiring opening of a battery pack output contactor during a battery control module power-up, it is possible to increase the probability that a controller external to the battery pack is operating in a desired mode before closing the battery pack output contactor. For example, if a battery controller experiences a power-up condition, it may be judged by the battery controller that a controller external to the battery pack is operating as expected when the first instruction from the external controller to the battery pack controller is an instruction to open a battery pack output contactor. When the battery pack controller receives the expected opening instruction, the probability increases that the vehicle controller has set the vehicle power bus in a desired state before charge from the battery pack is applied to the vehicle power bus. In this way, the possibility of applying battery power to the vehicle bus before the vehicle bus is ready to receive power may be reduced.
The present description may provide several advantages. In particular, the method can reduce the possibility of connecting battery output to a vehicle voltage bus when the vehicle voltage bus is not configured to accept battery power. Further, the present description may reduce system cost since it requires no additional hardware.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.